The caution, from the main contractor CGI, warned of a number of open risks and issues for the HealthCare.gov web site even as company executives were testifying publicly that the project had achieved key milestones.

On Capitol Hill on Tuesday, Medicaid Chief Marilyn Tavenner, whose job it was to oversee the October 1 rollout of the website, said she did not foresee its problems.

"No, we had tested the website and we were comfortable with its performance," she said. "Now, like I said, we knew all along there would be as with any new website, some individual glitches we would have to work out. But, the volume issue and the creation of account issues was not anticipated and obviously took us by surprise. And did not show up in testing."

But the CGI document, which describes "top risks currently open" and "outstanding issues currently being mitigated" says the testing timeframes are "not adequate to complete full functional, system, and integration testing activities" and lists the impact of the problems as "significant."

CGI had no comment other than to confirm authenticity of the report that also gave "the highest priority" and warns "we don't have access to monitoring tools" and "hub services are intermittently unavailable" -- short for the "site's not working sometimes."

One concern, listed as "severe," warned, "CGI does not have access to necessary tools to manage envs in test, imp, and prod. Specifically (1) we don't have access to central log collection / view (2) we don't have access to monitoring tools. We have repeatedly asked CMS and URS but have not been granted this access."

The report, which documents issues from August 2013 and was sent to at least one employee at CMS by an executive at CGI on September 6, was submitted in response to a request by the House Oversight Committee, which is now investigating the rollout of the health law.

CMS pointed to part of the report that said all "upcoming major milestones" were seen as "on track."

Brian Cook, an agency spokesman, said the report was "not a dire warning" but more of a "list of things to do" if read in full.

"What's been done, what needs to be done, what needs to be resolved. It is misleading to cherry pick a few lines," he said, adding that the report identified issues and "we worked to address those issues and all issues identified."

It is not clear if a later report detailed that the issues were resolved. But the warnings run counter to Health Secretary Kathleen Sebelius' stated optimism to CNN's Sanjay Gupta that when she woke up October 1, things would go smoothly.

Cheryl Campbell, a Senior Vice President for CGI Federal told lawmakers on Capitol Hill October 25, "no one ever gets enough time for testing."

Campbell, whose company has a contract worth a possible total of more than $200 million for its work on the system, noted than an end-to-end test conducted within two weeks of the launch caused the system to crash. She said it was up to CMS to decide on proceeding with the rollout.

Campbell did not raise any alarm bells on Capitol Hill back in September, when she told a House Committee CGI was confident it could get the job done.

"To date, the marketplace implementation has achieved all of its key milestones from the initial architecture review in October 2011 to project baseline review in March 2012 and, most recently, the operational readiness review in September 2013," before the website went live.

Up on Capitol Hill on Tuesday, Tavenner, kicked off testimony by saying she's sorry for the Obamacare rollout.

"We know that consumers are eager to purchase this coverage and to the millions of Americans who have attempted to use healthcare.gov to shop and enroll in healthcare coverage," she said. "I want to apologize to you that the website has not worked as well as it should."

It was a big switch from August, before CGI's report, when Tavenner told lawmakers the rollout was "on track."

"CMS is ready for October 1 and we're motivated and ready for the hard work ahead," she said at that time.